Oxygen breathing devices of this type are used to supply oxygen to passenger of an aircraft in an emergency situation like decompression of the cabin of such an aircraft. In such case, oxygen masks are provided to the passenger, usually by opening a cover lid of a casing accommodating the components of such oxygen breathing device arranged above the passenger in the ceiling and dropping out the mask. Either in the course of opening said cover lid or by an additional action like pulling an oxygen supply line the oxygen flow from the oxygen source to the oxygen mask is started.
An example of such an oxygen mask is shown in U.S. Pat. No. 5,265,597. Said oxygen mask is connected to an oxygen bag serving to modulate the continuous oxygen flow from the oxygen source to the low pressure side and the periodic inspiration and expiration cycle of the passenger. By this, the individual breathing cycle of each passenger is satisfied by the oxygen supply system in that a continuous flow of oxygen is directed into the oxygen bag and the passenger is allowed to periodically inhale said oxygen from the oxygen bag.
WO 2006/086044 A2 shows another oxygen conservation system for commercial aircraft. In this system, a plurality of oxygen masks are provided, each mask eing associated with a respective plurality of reservoir bags attached to said masks. All reservoir bags are connected to a single oxygen source consisting of one or more cylinders of compressed oxygen. The system such disclosed allows for providing oxygen to a plurality of passengers and at the same times allows each passenger to conduct his individual breathing cycle of inspiration and expiration.
EP 2 127 700 A1 discloses an oxygen breathing mask associated with an oxygen bag which is adapted to provide oxygen out of the oxygen bag to the passenger in a first section of the inspiration cycle and to thereafter provide ambient air to the passenger in a second section of the inspiration cycle. By this, the consumption of oxygen can be reduced significantly without negatively affecting the oxygen uptake by the passenger since breathing air inhaled in a late cycle of the inspiration usually does not reach the lung of the passenger and thus cannot be used for oxygen transfer into the blood of the passenger.
Finally, EP 2 127 699 A1 and U.S. Pat. No. 3,981,300 A disclose oxygen breathing systems wherein oxygen is produced by a chemical oxygen generator and buffered in a pressure tank. These devices, however, are bulky and heavy and thus increase the space requirement and weight of modern commercial aircraft.
A problem associated with oxygen supply systems as described above is, however, the control of oxygen flow in view of the desire to prove a compact design of the system. In practice, either oxygen pressure tanks or chemical oxygen generators are used as an oxygen source since these oxygen sources allow for a compact design and ensure a save storage of the oxygen over a long period of time.
However, the chemical reaction leading to the production of oxygen often cannot be controlled in such a way as to generate a constant oxygen flow but may rather produce a pulsatile flow with a short pulse frequency or may produce an inconstant flow over the whole time of oxygen production in that a period of higher or lower oxygen production may occur at the beginning, in the middle or at the end of the chemical reaction. Similarly, oxygen flow from pressure tanks may undergo such pulsatile flow in that a control valve used to control said flow leads to such pulses or in that due to the constant reduction of the inside pressure following the release of the oxygen the flow rate is not continuous over the whole time of oxygen supply. Still further, mechanical influences like shaking, vibrations acting onto the whole oxygen supply system may produce such pulsatile flow phenomena or variations in the voltage or current of an electrical energy supply system used to control the oxygen flow may result in such pulses. In particular in an emergency situation, such mechanical or electrical influences may be present and thus negatively affect the oxygen supply to the passenger.
A general problem associated with such emergency oxygen supply systems for passenger of an aircraft is resulting from the fact that in modern large commercial aircraft a very large number of such oxygen supply systems must be provided. Whereas in practice two or three passengers are supplied via separate masks from one common oxygen source, the overall weight of the emergency oxygen device and the space required for arranging such device into the aircraft cabin considerably affects the total performance of the aircraft by its weight and the cabin space required for it. Thus, a general object associated with such emergency oxygen systems for passengers in a commercial aircraft is the desire to reduce the space required to arrange such system in the cabin and the weight of such system.